Department of Chemistry, Youngstown State University, Youngstown, Ohio 44555, USA.
J Phys Chem A. 2010 Mar 18;114(10):3713-7. doi: 10.1021/jp1003159.
C(2)F(4) coupling constants have been evaluated at EOM-CCSD/(qzp,qz2p) in binary complexes with electron donors X (X = HLi, Cl(-), CN(-)) and with the electron acceptor FH, and in ternary complexes FH:C(2)F(4):X in which X and FH are located on opposite faces of the C(2)F(4) pi cloud. The electron donors X and the electron acceptor FH have opposite effects on (1)J(C-C), (1)J(C-F), (2)J(C-F), and (3)J(F-F) in binary complexes. Effects of X and FH on a particular coupling constant in a ternary complex are additive if the change in the coupling constant in this complex relative to C(2)F(4) is within 1 Hz of the sum of the changes in the corresponding binary complexes. This is the case for (1)J(C-F). Both positive and negative nonadditivities are computed for the remaining coupling constants. Although the values of most coupling constants lie between the values for FH:C(2)F(4) and C(2)F(4):X, that is not the case for (2)J(C-F), and the effect of FH is enhanced by the presence of X. Moreover, values of (3)J(F-F) trans and cis for FH:C(2)F(4):X when X is Cl(-) or CN(-) bonded through C are within 1 Hz of the values for the corresponding binary complex C(2)F(4):X. Significant differences can be found between the relative contributions of the PSO, FC, and SD terms to total J and to the nonadditivities of J in ternary complexes FH:C(2)F(4):X.
C(2)F(4) 偶合常数已在 EOM-CCSD/(qzp,qz2p) 水平下，于与电子给体 X（X = HLi、Cl(-)、CN(-)）形成的二元复合物，以及与电子受体 FH 形成的二元复合物中进行了评估，在其中 X 和 FH 位于 C(2)F(4)π 云的相对两侧的三元复合物 FH:C(2)F(4):X 中也进行了评估。电子给体 X 和电子受体 FH 对二元复合物中的 (1)J(C-C)、(1)J(C-F)、(2)J(C-F) 和 (3)J(F-F) 有相反的影响。如果三元复合物中相对于 C(2)F(4) 的耦合常数的变化在 1 Hz 内，则 X 和 FH 对特定耦合常数的影响是可加的，该变化与相应二元复合物中的变化之和相对应。对于 (1)J(C-F) 就是这种情况。对于其余的耦合常数，计算出了正的和负的不可加性。尽管大多数耦合常数的值介于 FH:C(2)F(4) 和 C(2)F(4):X 的值之间，但 (2)J(C-F) 并非如此，并且 FH 的影响会因 X 的存在而增强。此外，当 X 通过 C 与 Cl(-) 或 CN(-) 键合时，FH:C(2)F(4):X 的 (3)J(F-F)trans 和 cis 值与相应二元复合物 C(2)F(4):X 的值相差 1 Hz。在三元复合物 FH:C(2)F(4):X 中，PSO、FC 和 SD 项对总 J 和 J 的不可加性的相对贡献有显著差异。
